The invention relates to a locking device of a longitudinal, i.e. lengthwise adjustment device of a vehicle seat. The locking device is provided, on the one side, with a catch bar having periodically alternating snap openings and snap studs. The catch bar is assigned to a bottom rail of the longitudinal adjustment device. On the other side, the locking device is provided with a locking unit assigned to a seat rail of the longitudinal adjustment device. The locking unit has at least two locking pins that can be inserted into snap openings independent of one another and can jointly be retracted therefrom. The locking pins are arranged in a guide member having a pin bore for each locking pin.
Such a locking device has been previously proposed in DE 197 09 149 A. Further relevant prior art is also described in EP 408 932 B and DE 27 29 770 C. This type of looking device is also termed a multiple pin locking device. These devices permit a fine pitched and sensitive longitudinal adjustment. In the locked position, a lacking pin fits beside a snap stud. Usually, it is a sloping side of the locking pin that fits beside a snap stud. The sloping sides are formed by truncated regions on the free end of the locking pins for example. A locking pin locks in one direction of displacement. Another locking pin looks in the other direction of displacement.
Since generally but one locking pin is responsible for locking one direction of displacement, under crash load all of the locking forces act onto that one locking pin and onto the corresponding snap stud on which the locking pin is resting. Under high load conditions, the corresponding forces intentionally cause the locking pin to bend, as has already been described in DE 197 09 149 A mentioned herein above. Now, if a locking pin bends, the angle between the locking flank thereof and the snap stud changes. The angle increases. Before, it was within the range of self-locking, but after bending, it may be outside of this range. If it is outside of this range, said forces exerted onto the locking pin can push the locking pin upward, meaning out of the locking condition. The locking pin must however be prevented from disengaging from the corresponding snap stud in order not to release the locking state.
This is where the invention comes to bear. The object of the invention is to further develop the locking device of the type mentioned herein above in such a manner that the locking pins are prevented from being pushed upward out of a locking position in an accident situation.
In view of the locking device of the type mentioned herein above, the solution to this object is to provide at least one of the snap pins with a grooved region and to locate said grooved region in proximity to a lower end of the corresponding pin bore when the snap pin is engaged in one of the snap openings.
At least one of the locking pins, preferably all of the locking pins, have a grooved region which is also termed crash groove or fluting. Several individual grooves may be located in the region of this crash groove. Preferably, three to five individual grooves are provided. In the region of the grooves, the locking pin is tapered, preferably slightly tapered, e.g., by between 5 and 15%, preferably by about 8%. Moreover, toward the free end of the locking pin, the crash groove preferably has a sharp-edged transition where it more specifically forms an edge or a stop face.
The fluting formed by one or several individual grooves efficiently prevents the locking pin from being pushed upward out of its locking position in an impulse-like or in a slow manner. As soon as the locking pin is slightly bent in the event of an accident, the one individual groove, or the several individual grooves, provide many possibilities for interlocked and clutched engagement. Several individual grooves that may interact with the material of the guide member at the lower end of the pin bore are preferably available so that the locking pin is prevented from moving upward.
The fluting also slightly weakens locally the locking pins so that these preferably warp in the region of the fluting. This is where the locking pins also offer the largest area for abutment on the region about the lower end of the pin bore.
The reduction in the diameter of the locking pins in the region of the fluting is chosen, on the one side, to be great enough, so that the stop face provided is great enough to provide a good mechanical interlock and, on the other side, is chosen not so great that the locking pin is markedly weakened and risks to break in the region of the fluting in the event of an accident. What is wanted is a selective deformation in the region of the fluting.
In a preferred development of the invention, the guide member has a projection pointing downward, i.e., toward the catch bar, for each pin bore. The projections extend as a continuation of the respective one of the pin bores. The projections are preferably annular. They allow for softer and more flexible guidance of the locking pins than in the region of the pin bore of the guide member. They offer less resistance than the guide member to outward lateral bending. Under crash load, the projections may be bent. As a result thereof, the interlocked engagement with the fluting is enhanced.
In an improved embodiment of the invention it is suggested to configure the projections to form rimmed holes. For this purpose, one pilot hole for each pin bore is first made in the guide member, said pilot hole having a diameter which is considerably smaller than that of the completed pin bore and amounts to 60% of the diameter of the completed pin bore for example. Now, the pilot hole is enlarged by means of a punch the outer dimensions of which correspond to the pin bore, a respective projection being formed in the process. The projections are connected to, and integral with, the guide member. In another embodiment, the projections may be realized by separately inserting a material, such as slide bushes for example.
It proved particularly advantageous to provide a bead in the catch bar, said bead being curved upward toward the guide member. As a result thereof, the catch bar is mechanically reinforced and the stability of a locking condition increased. The bead may comprise any cross section, such as semi-circular, triangular or trapezoidal, and so on.
In a preferred embodiment, three or four almost evenly spaced individual grooves are provided side by side. The individual grooves preferably have a truncated bottom that tapers toward the free end of the locking pin. At their free ends, the locking pins advantageously have a short, cylindrical front end.
It finally proved advantageous to configure the locking pins to have a round shape, but the pin bores to have a non round shape. This more specifically applies to the region of the projections. Under a defined load, the material about the pin bore, and more specifically the projections, may plastically deform. As a result thereof, the edges of the individual grooves are allowed to better engage into the projection.
Further advantages and characteristics of the invention will become apparent in the other claims and in the following non restrictive description of embodiments given by way of example only with reference to the drawing.